Solvents for gasoline inhibitors



Fatented Mar. 18, 1952 2,589,979 I SOLVENTS FOR GASOLINE INHIBITORS Barney R. Strickland, Westfield, N. J assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application September 1, 1949, Serial No. 113,663

2 Claims.

This invention relates to the use of improved solvents for use with gasoline inhibitors. In accordance with the present invention, toluene or dioxan (diethylene dioxide) also known as paradioxan is employed to dissolve the inhibitors which are conventionally added to gasolines. This application constitutes a continuation in part of U. S. No. 790,223, filed December 6, 1947 now abandoned, which discloses the subject matter of this application.

In order to prevent the oxidation of potential gum forming substances in gasolines, and in order to prevent discoloration of the gasoline, both of which may occur, it is conventional practice to add various inhibitors to the gasoline. These inhibitors are of various types, for example, aminophenols, phenylenediamines, alpha-naphthol, trialkylphenols, and straight chain alkyl phenols. In general these inhibitors are somewhat unstable being subject to decomposition over a period of time, chiefly due to their reaction with air or oxygen. In particular, the aminophenols and the phenylenediamines are subject to degradation by oxidation. It is a particular object of this invention to minimize the degradation of these gasoline inhibitors by minimizing their tendency to react with oxygen.

It is essential that an inhibitor used with gasoline be reasonably soluble in the gasoline. This is a particularly stringent requirement in view of the present use of gasolines at extremely high altitudes and the consequently low temperatures. Consequently, it is general practice to dissolve the inhibitors in a suitable solvent prior to addition to the gasoline so as to improve the solubility of the inhibitors in the gasoline. At the present time alcohols are generally employed as the solvent, being soluble in gasolines, and being a goodsolvent for the inhibitors generally used. It is a further object of this invention that improved solvent action be obtained by the use of toluene or dioxan in place of the alcohols conventionally used. In view of the present Wide commercial use of alcohol as the solvent for the inhibitors, this disclosure will be especially directed to show the improvement of the present solvents over alcohol.

To determine the relative solubility of inhibitors in alcohol and in the solvents employed in this invention, a typical inhibitor 2,6-ditertiarybutyl-4-methylphenol was added to difierent alcohols and to toluene at 75 F. It was found that less than wet. percent of the inhibitor could be dissolved in isopropyl alcohol, that 21% of the inhibitor could be dissolved in normal butylalcohol, that 25% of the inhibitor could be dissolved in ethyl alcohol, and that 41% of the inhibitor could be dissolved in toluene. Further data obtained indicated that substantially 35% by weight of the inhibitor named could be dissolved in toluene without danger of crystallizing out at 0 F.

In addition to the high solvent power of toluene this solvent is advantageous in that it is relatively inexpensive and has a very high motor fuel blending value.

A still further advantage of toluene is that it is in some way effective in minimizing the air oxidation of solutions of the inhibitors. This is indicated by the following table:

Table I Time required for Indicated Oxygen Pressure Drop at.-

The data were obtained by containing the inhibitor and solvent in an A. S. T. M. breakdown bomb. The solutions were subjected in the bomb to lb. oxygen pressure and to temperatures of F. and 212 F. The time required for the pressure in the bomb to drop 5 lbs., and 10 lbs., was recorded. This time represents the time required for sufiicient oxygen to react with the solutions to create the indicated pressure drop. It will be noted that the solution of the inhibitor in ethyl alcohol was subject to comparatively rapid oxidation, the oxygen pressure in the bomb dropping 5 lbs. in 240 minutes at 150 F. When the inhibitor was dissolved in toluene, however, more than 1400 minutes were required to obtain the same drop in oxygen pressure. At 212 F. the corresponding times for 5 lbs. pressure drop were 90 minutes with ethyl alcohol and 840 minutes for toluene. These data clearly indicates that the toluene when used as the solvent has a profound effect on the reactivity of the inhibitor with air. Further experiments showed that neither the alcohol or toluene alone reacted with oxygen under the test conditions.

Further experiments were conducted with other inhibitors under difierent test conditions. An inhibitor consisting of N,N'-di-sec-butyl-pphenylenediamine was dissolved in the particular solvent to be tested in a concentration of 15 grams per 100 ml. of solution. The solution of the inhibitor was then introduced into a closed system, comprising a packed tower maintained at room temperature and atmospheric air pressure, wherein it was circulated countercurrently to a stream of air. The results obtained are indicated in Table II below:

The data showing the milliliters of oxygen absorbed by the solution were obtained by analytical methods to determine the oxygen absorption. It will be noted that the inhibitor dissolved in ethyl alcohol was extremely reactive with oxygen, absorbing 2900 ml. or oxygen in 200 hours, under the test conditions. The inhibitor dissolved in toluene, however, was comparatively unreactive with oxygen only absorbing 120 mlpafter 200 hours. Considerable improvement in oxygen reactivity was notable in the case where 9 parts of toluene were used with one part of ethyl alcohol. In the first case, where the inhibitor was dissolved in ethyl alcohol, degradation was so extensive that'the inhibitor became very dark and tarry and completely lost its inhibiting potency. On the other hand, the inhibitor dissolved in toluene darkened only slightly and did not materially lose its inhibiting potency. The inhibitor oxidized in toluene solution was found by analysis to contain 95% active inhibitor. 7 7

Further tests were made on a variety of inhibitors in difierent solvents employing A. S. T. M. breakdown bombs at a temperature of 150 F. and 30 lbs. per square inch gauge oxygen pressure. The results obtained are indicated in Table III:

Table III Time, Minutes, for Oxygen sample Pressure Droplbs. 10 lbs.

' N,N'-di-sec-butyl-p-phenylenediamine alone no solvent 270 510 N,N-di-sec-butyl-p-phenylenediamine Methyl alcohol 4O 55 Ethyl alcohol 55 90 Methyl propyl ketone 120 175 Benzene... 190 265 Toluene et 130 V 190 Xylene 250 355 Isooctane 325' 535 Cyclohexane 405 635 Diiso'butylene.- 280 475 Dioxan 730 985 n-butylrp'aminophenol Methyl alcohol 25 45 Isopropyl alcohol 65 110 Methyl propyl ketone 55 80 'Dioxan 120 195 will be-noted from the data of Table III that the inhibitors employed were markedly'less reactive with oxygen when dissolved in dioxan than in any of the other solvents employed. Thus for example in 55 minutes the oxygen bomb pressure has dropped 5 lbs. when N,N'-di-sec-butyl-pphenylenediamine was dissolved in ethyl alcohol, while 730 minutes were required to obtain this same pressure drop when the inhibitor was dissolved in dioxan. The reactivity of the second inhibitor tested, normal butyl-p-aminophenol was similarly improved as indicated by the data for solutions in alcohol and dioxan.

To further indicate the unexpected advantages of employing 'tolueneand dioxan as the solvents "for inhibitors, N,N'-di-sec-butyl-phenylenediamine was dissolved in Various solvents in a concentration of 15 grams per ml. of solution and was allowed to stand at room temperature in closed bottles containing an oxygen atmosphere for a period of two days. Results of this test are given in Table IV:

Table IV Appearancegigg g, of

i itor osolvent After tency Lost Initially 2 Days After 2 Days Clear Dark '77 d0 'clo 03 do Clear. '6 Dioxan do .do. 3

correspond to dissolving the inhibitor in an olefinic gasoline. The inhibitor employed was N,N-di-sec butyl-p-phenylenediamine. Standard solutions of this inhibitor in different solvents were .prepared at a concentration of 2.4 mg. of inhibitor per ml. of solution. These solutions .were then added to diisobutylene to provide a concentration of 0.'5.-and 1 lb. of inhibitor per- 5000 .gallons of diiso'butylene. The inhibited diisobutylene was .then subjected to a .standard A. S. T. M. breakdown test in which the solution tested was placed in anA. S. LM. bomb at 212 F. under 100 lbs. .per squareinch oxygen pressure. The number of minutes were determined for the bomb to reach acondition at whichthe pressure drop in the bomb was equal to 2 lbs/sq. in. per 15 minutes. The resriltsof this test are given in Table V:

-Ta'.bZe V lbs. of N,N-di-seo-butyl-p-phcnylenedlemme/5000 ai gallons Diisobutylene gg Uninhibited Diisobutylene 85 .5 lbs dissolved inMethylAlcohoL 980 1.0 lbs. dlssolved in Methyl ,Alcohol 1,360 .5 lbs-dissolved in Ethyl Alcohol. l, 1.0 lbs. dissolved-in Ethyl Alcohol. 1, 440+ .5 lbs. dissolved'inToluene 1, 440+ 1.0 lbs. dissolved in'Toluene" 1 440+ .5'lbs.-dissolved. in.Dioxan 1, 440+ 1; 440+ 1:0 lbs. dissolvedin Dioxan It will be noted from this data that uninhibited diisobutylene is readily oxidized, giving a breakdown time of only 85 minutes. The oxidation is inhibited to some extent when the inhibitor is added in solution with either methyl or ethyl alcohol. However when the inhibitor is added in solution with either toluene or dioxan considerably greater inhibiting potency may be appreciated. Thus only .5 lbs. of the inhibitorper 5000 gallons of diisobutylene, when initially dissolved in toluene or dioxan, is considerably more eflective than either 0.5 lbs. of the inhibitor dissolved in methyl or ethyl alcohol or even 1 lb. dissolved in methyl alcohol. Similarly this is as efiective as 1 lb. of the inhibitor dissolved in ethyl alcohol. It will thus be seen that use of toluene or dioxan as the solvent for the inhibitor results in inhibiting action of improved potency.

is preferred that 25-100 weight per cent of inhibitor based on the solvent be dissolved in the solvent the inhibitor concentrates thus consist of compositions containing about 20 to 50% of inhibitor based on the total composition. The solution of the inhibitor in the solvent may then about 1 to 4 times the amount of N-N'-di-secondary-butyl p-phenylenediamine.

2. A motor fuel inhibitor concentrate substantially stable to oxygen containing gases which consists of para-dioxan containing about 20 to of N -N-di-secondary-butyl p-phenylenediamine.

BARNEY R. S'IRICKLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,380,420 Emerson July 31, 1945 2,443,569 Ruggles June 15, 1948 OTHER REFERENCES Fieser and Fieser, Organic Chemistry, D. C. Heath 8: 00., Boston, Mass. (1944) p 126. 

1. A COMPOSITION COMPRISING A MOTOR GASOLINE, A N-N''-DI-SECONDARY-BUTYL P-PHENYLENEDIAMINE AND PARA-DIOXAN, SAID N-N''-DI-SECONDARY-BUTYL P-PHENYLENEDIAMINE BEING PRESENT IN PROPORTIONS OF ABOUT 0.1 TO 4 POUNDS PER 5000 GALLONS, AND SAID PARA-DIOXAN BEING PRESENT IN PROPORTIONS OF ABOUT 1 TO 4 TIMES THE AMOUNT OF N-N''-DI-SECONDARY-BUTYL P-PHENYLENEDIAMINE. 